About Optics & Photonics TopicsOSA Publishing developed the Optics and Photonics Topics to help organize its diverse content more accurately by topic area. This topic browser contains over 2400 terms and is organized in a three-level hierarchy. Read more.

Topics can be refined further in the search results. The Topic facet will reveal the high-level topics associated with the articles returned in the search results.

Abstract

This paper proposes a sub-aperture correlation based numerical phase correction method for interferometric full field imaging systems provided the complex object field information can be extracted. This method corrects for the wavefront aberration at the pupil/ Fourier transform plane without the need of any adaptive optics, spatial light modulators (SLM) and additional cameras. We show that this method does not require the knowledge of any system parameters. In the simulation study, we consider a full field swept source OCT (FF SSOCT) system to show the working principle of the algorithm. Experimental results are presented for a technical and biological sample to demonstrate the proof of the principle.

Figures (11)

Schematic diagram for the interferometric setup. Lens L1 and L2 form a 4-f telecentric imaging system. Dotted rays show the imaging path of a point on the object in focus. Camera is at the focal plane of lens L1.

Segmentation of Fourier data into KxK subapertures with K = 3. Green square dots represent sampling points of the average local slope data due to non-overlapping subapertures. Red dotted boxes represent subapertures with about 50% overlap in both directions. Blue circular dots represent sampling points of the slope data due to overlapping subapertures. With overlapping subapertures we can increase the sampling points to reduce the error in phase estimation.

(a), (b), (c) and (g) show the phase corrected images for non-overlapping subaperture with values of K equal to 3, 5, 7 and 9 respectively, and (d), (e), (f) and (j) are the respective residual phase error in radians. (h) and (i) are the images for subapertures with 50 percent overlap for K equal to 3 and 5, and (k) and (l) are the respective residual phase error in radians.

RMS residual phase error in radians for different values of K and different percentage of overlap between subapertures. For the same value of K the size of subapertures in non- overlapping and overlapping cases are the same.

(a) Schematic of the experimental setup: M is the mirror, B.S. is the beam splitter, MO is the 5X NIR microscope objective, L1 and L2 are lens with focal length f = 200 mm, L3 and L4 are lens with f = 150 mm and 75 mm and P is the pupil places at the focal plane of L3 and L4, (b) sample consisting of layer of plastic sheet, film of dried milk and the RTT, (c) image of the RTT surface obtained with non-uniform plastic sheeting, (d) Fourier transform of the image shows it is band limited, and (e) zoomed in image of (c) showing 390×390 pixels . Focus was placed on the RTT.

Phase corrected images of the one in Fig. 7, obtained using (a) non-overlapping subapertures with K = 3, (b) non-overlapping subapertures with K = 5 and (c) overlapping subapertures with K = 5. (d), (e) and (f) are the detected phase error across the aperture in radians in the case of (a), (b) and (c) respectively.

(a) A tomogram of the grape sample, (b) 3-D image volume with dotted line showing location of the tomogram shown in (a), (c) enface image obtained at the depth of 424.8 µm in the grape sample indicated by arrow in (a), (d) is the digitally focused image of (c).